Vinyl chloride polymer/neopentyl glycol bis(diphenyl phosphate) compositions

ABSTRACT

A vinyl chloride resin composition contains, as the major plasticizer, a neopentyl glycol bis(diphenyl phosphate) composition in an amount that is no less than about 25% by weight, based upon the vinyl chloride resin being present at 100%, by weight.

Triaryl phosphate esters (for example, tricresyl phosphate) arerecognized as one of the earliest primary commercial plasticizers forflexible vinyl chloride resins (hereinafter also referred to as “PVC”).These plasticizers are still used in vinyl composites to aid inconferring flexibility upon such compositions, but their maincontribution is in regard to flame retardancy. Careful selection of theappropriate phosphate esters is critical for affecting the desireddegree of flame retardancy. Trialkyl phosphates are too volatile formost vinyl applications. Triaryl phosphates are excellent flameretardant plasticizers but may generate too much smoke to pass currentbuilding codes and standards (namely, ASTM-E-84, the Steiner Tunneltest). Alkyl diphenyl phosphates, although slightly less effective asflame retardants, have, because of their alkyl side chain, thecharacteristic of producing less smoke in vinyl formulations since theyhave a lowers phenolic moiety content, which is well known forgenerating smoke. In fact, there is sufficient proof that slightlyincreasing the aliphatic chain length contributes to lower smokegeneration.

Often, the effort to improve flame resistance is counterproductive tolow smoke generation characteristics since these two phenomena can bethe result of competing mechanisms. Flame retardants can interfere withthe efficacy of the combustion of volatile species and can cause sootyair-borne particles to be formed, while low smoking composites cancreate higher heats of combustion to more efficiency consume combustibleorganic gases.

Certain disclosures that are relevant to the present invention exist inthe prior art concerning blending a vinyl chloride resin with branchedalkylene glycol bis(diphenyl phosphate) compositions. For example,British Patent No. 2,061,949 describes the addition of suchbisphosphates at amounts of up to 10 parts by weight of bisphosphate per100 parts by weight of vinyl chloride resin. Somewhat higher amounts ofsuch bisphosphates (namely, up to about 20 wt % per 100 parts by weightof vinyl resin) are shown in Japanese Patent Publication No. 40342/74,but only in the presence of significantly higher amounts (30 wt % to 50Wt %) of another, more conventional plasticizer (e.g., dioctylphthalate). Finally, while U.S. Pat. No. 3,869,526 to M. Combey et al.also described the use of these bisphosphates, it specifically excludesthose that contain aryl substitution of six to eight carbon atoms on allfour —OR substituents attached to the two phosphorus atoms. Thisexcludes, for example, neopentyl glycol bis(diphenyl phosphate)compositions from selection for use in the Combey invention.

The present invention relates to the use of a neopentyl glycolbis(diphenyl phosphate) composition, as the major plasticizing additive,to function as a very effective flame retardant in PVC composites, whenused in amounts that are no less that about 25 wt %, by weight of thePVC (for example, from about 35 wt % to about 125 wt %, as exemplifiedby use at from about 40 wt % to about 90 wt % by weight of the PVC)while also contributing significantly less smoke than does arepresentative triaryl monophosphate ester. The flexibility of theresulting composition that is imparted to vinyl compounds by use of thepresent invention is similar to that obtained by use of a triarylphosphate plasticizer. While other plasticizing additives can be alsopresent in the composition, they will be present in lower amount thanthe amount of neopentyl glycol bis(diphenyl phosphate) composition.

EXAMPLES

Vinyl Formulations Components 1 2 3 4 S-PVC (K = 71) 100 100 100 100INTERLITE ZG6067/3 5 5 5 5 ESTABEX E2307 2 2 2 2 PHOSFLEX 390 60 NPGDP60 60 60 Zinc Borate 6 6 AOM LS030 6

The vinyl resin used was a suspension type PVC with a K value of 71. TheINTERLITE brand stabilizer (from Akcros) was a mixture of metal soaps,antioxidants and acid scavengers and the ESTABEX 2307 brand product(also from Akcros) was a epoxy stabilizer. The phosphate esters used inthis evaluation were: PHOSFLEX 390 brand (P-390) from Akzo NobelFunctional Chemicals LLC, an alkyl diphenyl phosphate commonly used inwire and cable applications as a flame retardant/plasticizer; and“NGPDP”, which represents neopenytl glycol bis(diphenyl phosphate). Alsoincluded in this screening experiment were certain common flameretardant synergists and smoke suppressants, namely, zinc borate (fromJ. Storey) and ammonium octamolybdate (AOM LS030 brand).

The above formulations were compounded on a two-roll mill for asufficient time to achieve homogeneity. The milled sheets werecompression molded to specimen size to perform cone calorimeteranalysis. The results are as follows:

Cone Calorimeter Study of Phosphate Esters in Vinyl

Composite No.: 1 2 3 4 Plasticizer P-390 NPGDP NPGDP NPGDP Zinc borate —— 6 6 AOM — — — 6 Cone Data* Peak Heat Release Rate 261.36 205.86 165.21158.32 (PHRR) Avg. Specific Extinction 1126.33 1135.85 1037.72 1039.69Area Time To Ignition (TTI) 16.97 22.31 26.16 22.17 Fire PerformanceIndex 0.065 0.108 0.158 0.140 Smoke Parameter 294 234 171 165 CO 0.1330.160 0.125 0.111 CO₂ 1.328 1.280 1.372 1.413 *Cone Calorimeter: 50kW/m² heat fluxDiscussion of Composite Testing Results:

Compared with the control flame retardant plasticizer, PHOSFLEX 390brand (Ccomposite No. 1), the cone flammability data suggests that NPGDP(No. 2), at equivalent levels, performs as well or better in low smokegeneration (see the lower specific extinction area—“SEA”) and has asignificantly less peak heat release rate than isodecyl diphenylphosphate. Both the heat release rate and smoke generation of neopentylglycol bis(diphenyl phosphate)/vinyl composites were further improvedwith the addition of zinc borate (see Composite Nos. 3 and 4).Converting this information into calculated values such as the “fireperformance index” (the time to ignition divided by the peak heatrelease rate—a higher value implies greater fire performance)demonstrated significantly better performance than the use of neatP-390. Another calculated reference, the “smoke parameter” is derivedfrom calculations of the peak heat release rate times the specificextinction area (smoke obscuration) divided by 1000 (lower value impliesimproved low smoke efficiency). The addition of the smoke suppressantammonium octamolybdate (No. 4), showed a slight improvement to low smokegeneration but is not considered to have a significant influence on thefire or smoke performance of the composite.

Although the use of neopentylene bis (diphenyl phosphate) as the sole FRadditive showed low smoke and high flame retardant efficacy in vinylcomposites, such characteristics can be further boosted in the presenceof certain additional flame retardant additives. For example, theaddition of zinc borate and ammonium octamolybdate have shown anexceptional boost in flame resistance and low smoke generation whenblended with the aforementioned alkylene bridged bisphosphate (seeFormulation Nos. 5 and 6, which are in accordance with the presentinvention, in the first Table set forth below). At fifty parts perhundred (phr) of plasticizer in a flexible vinyl formulation, asignificant reduction of smoke generation was seen (about a twenty-eightpercent decrease).

Similarly formulated composites using another monophosphate ester (i.e.,the SANTICIZER 2148 brand product, an alkylated diphenyl phosphate, fromFerro) and certain non-FR plasticizer types (DINP, diisononyl phthalate,from Exxon and TOTM, trioctyl trimellitate, from Sunoco), although insome cases demonstrating low smoke values, do not match the low smokeperformance seen with combinations of the inorganics with thealkylene-bridged bisphosphate NPGDP (see the second Table set forthbelow).

Formulation Nos.: 5 6 7 8 9 10 PVC (k value = 71) 100 100 100 100 100100 CaCO3 10 10 10 10 10 10 Alumina Trihydrate (Hydral 710) 30 30 30 3030 30 Zinc Borate 6 6 6 6 6 AOM 6 6 6 6 6 NPGDP 50 50 TOTM 50 SANTICIZER2148 50 DINP 50 PHOSFLEX 31L 50 Epoxidized Soybean Oil (ESO) 5 5 5 5 5 5Dibasic Lead Phthalate (DYTHAL) 5 5 5 5 5 5 BZ-4975 2.5 2.5 2.5 2.5 2.52.5 Totals: 202.5 214.5 214.5 214.5 214.5 214.5 Formulation Nos.: 5 6 78 9 10 NPGDP NPGDP/FRs DINP 31L S2148 TOTM Flammability LOI: 1.6 mm 3334 28 37.5 29 27.5 UL-94 (1.6 mm) V-0 V-0 FAIL V-0 V-0 V-1 (AFT) 00 >4″  0.1 0.5 2.6 Cone Calorimeter Results TTI 34.75 21.76 16.27 47.8518.13 17.53 PHRR 172.63 130.23 253.92 151.52 261.89 229.83 SpecificExtinction Area(Smoke) 806.17 582.15 791.75 958.24 809.44 715.02 FireProtection Index 0.201 0.167 0.064 0.316 0.069 0.076 Smoke Parameter 13976 201 145 212 164 Average CO₂ 0.8332 1.0563 0.9633 0.8459 1.0343 0.9891Average CO 0.1113 0.0575 0.0710 0.1089 0.0795 0.0795

The foregoing Examples have been presented to illustrate certainembodiments of the present invention and, for that reason should not beconstrued in a limiting sense. The scope of protection desired is setforth in the claims that follow.

1. A vinyl chloride resin composition that comprises as the majorplasticizer a neopentyl glycol bis(diphenyl phosphate) composition in anamount that is no less than about 25% by weight, based upon the vinylchloride resin being present at 100%, by weight.
 2. A composition asclaimed in claim 1 wherein the neopentyl glycol bis(diphenyl phosphate)composition is present at from about 35% to about 125%, by weight.
 3. Acomposition as claimed in claim 1 wherein the neopentyl glycolbis(diphenyl phosphate) composition is present at from about 40% toabout 90%, by weight.
 4. A composition as claimed in claim 1 whereinadditional flame retardant and smoke suppressant synergists are present.5. A composition as claimed in claim 4 wherein zinc borate isadditionally present.
 6. A composition as claimed in claim 4 whereinammonium octamolybdate is additionally present.
 7. A composition asclaimed in claim 2 wherein additional flame retardant and smokesuppressant synergists are present.
 8. A composition as claimed in claim3 wherein additional flame retardant and smoke suppressant synergistsare present.
 9. A composition as claimed in claim 8 wherein zinc borateis additionally present.
 10. A composition as claimed in claim 7 whereinzinc borate is additionally present.
 11. A composition as claimed inclaim 8 wherein ammonium octamolybdate is additionally present.
 12. Acomposition as claimed in claim 7 wherein ammonium octamolybdate isadditionally present.
 13. The composition as claimed in claim 5, whereinanimonium octamolybdate is additionally present.